1754

1754. Largest Merge Of Two Strings (Medium)

You are given two strings word1 and word2. You want to construct a string merge in the following way: while either word1 or word2 are non-empty, choose one of the following options:

• If word1 is non-empty, append the first character in word1 to merge and delete it from word1.

  <ul>
  	<li>For example, if <code>word1 = "abc" </code>and <code>merge = "dv"</code>, then after choosing this operation, <code>word1 = "bc"</code> and <code>merge = "dva"</code>.</li>
  </ul>
  </li>
  <li>If <code>word2</code> is non-empty, append the <strong>first</strong> character in <code>word2</code> to <code>merge</code> and delete it from <code>word2</code>.
  <ul>
  	<li>For example, if <code>word2 = "abc" </code>and <code>merge = ""</code>, then after choosing this operation, <code>word2 = "bc"</code> and <code>merge = "a"</code>.</li>
  </ul>
  </li>
  

Return the lexicographically largest merge you can construct.

A string a is lexicographically larger than a string b (of the same length) if in the first position where a and b differ, a has a character strictly larger than the corresponding character in b. For example, "abcd" is lexicographically larger than "abcc" because the first position they differ is at the fourth character, and d is greater than c.

 

Example 1:

Input: word1 = "cabaa", word2 = "bcaaa"
Output: "cbcabaaaaa"
Explanation: One way to get the lexicographically largest merge is:
- Take from word1: merge = "c", word1 = "abaa", word2 = "bcaaa"
- Take from word2: merge = "cb", word1 = "abaa", word2 = "caaa"
- Take from word2: merge = "cbc", word1 = "abaa", word2 = "aaa"
- Take from word1: merge = "cbca", word1 = "baa", word2 = "aaa"
- Take from word1: merge = "cbcab", word1 = "aa", word2 = "aaa"
- Append the remaining 5 a's from word1 and word2 at the end of merge.

Example 2:

Input: word1 = "abcabc", word2 = "abdcaba"
Output: "abdcabcabcaba"

 

Constraints:

• 1 <= word1.length, word2.length <= 3000
• word1 and word2 consist only of lowercase English letters.

Related Topics:
Greedy, Suffix Array

Solution 1.

// OJ: https://leetcode.com/problems/largest-merge-of-two-strings/
// Author: github.com/lzl124631x
// Time: O(N^2)
// Space: O(N)
class Solution {
public:
    string largestMerge(string word1, string word2) {
        priority_queue<string> q;
        q.push(word1);
        q.push(word2);
        string ans;
        while (q.size()) {
            auto s = q.top();
            q.pop();
            ans += s[0];
            if (s.size() > 1) q.push(s.substr(1));
        }
        return ans;
    }
};

TODO

find better solution